Comparative study of the partial oxidation of methane to synthesis gas in fixed-bed and fluidized-bed membrane reactors. Part II - Development of membranes and catalytic measurements

The catalytic partial oxidation of methane (CPOM) to synthesis gas was carried out in fixed-bed and fluidized-bed membrane reactors over a Ni/alpha-Al2O3 catalyst. For gas separation silicalite membranes inside an alumina and a porous stainless-steel matrix were synthesized and applied in the catalytic measurements. Moreover, a membrane obtained by deposition of palladium on the stainless-steel silicalite membrane was tested. The zeolite membranes were stable in the whole investigated temperature range (700<T<750 degrees C). The Pd-membrane was not stable; palladium layer did not withstand temperatures above 650 degrees C. In the catalytic measurements in the fixed-bed reactor and in the fluidized bed (P-CH4 = 66.6 kPa,P-O2 = 33.3 kPa, m(cat)/V=14 gs/ml) nearly thermodynamic equilibrium was achieved. However, neither in the fixed-bed reactor nor in the fluidized-bed membrane reactor an improvement in the syngas yield by means of the integrated product separation could be achieved. In the tired-bed membrane the unselective separation of methane was detrimental for methane conversion. In the fluidized-bed membrane reactor the amount of permeated hydrogen was not sufficient to shift significantly the equilibrium towards higher syngas yield. However, in the fluidized-bed membrane reactor significant better selectivities of separation were achieved. (C) 1998 Elsevier Science B.V.